Condensed Consolidated Balance Sheets - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Document Period End Date	Dec. 31, 2015
Document Fiscal Year Focus	2015	2014
Real estate assets:
Operating properties, net of accumulated depreciation of $352,350 and $324,543 in 2015 and 2014, respectively	$ 2,194,781,000	$ 2,181,684,000
Projects under development	27,890,000	91,615,000
Land	17,829,000	21,646,000
Total properties	2,240,500,000	2,294,945,000
Real Estate Held-for-sale	7,246,000	0
Cash and cash equivalents	2,003,000	0
Restricted cash	4,304,000	5,042,000
Notes and accounts receivable, net of allowance for doubtful accounts of $1,353 and $1,643 in 2015 and 2014, respectively	10,828,000	10,732,000
Deferred rents receivable	67,258,000	57,939,000
Investment in unconsolidated joint ventures	102,577,000	100,498,000
Intangible Assets, Net (Including Goodwill)	124,615,000	163,244,000
Other assets	38,472,000	34,930,000
Total assets	2,597,803,000	2,667,330,000
Liabilities:
Notes payable	721,293,000	792,344,000
Accounts payable and accrued expenses	71,739,000	76,240,000
Deferred Revenue, Current	29,788,000	23,277,000
Intangible Liabilities	59,592,000	70,020,000
Other liabilities	30,629,000	31,991,000
Disposal Group, Including Discontinued Operation, Liabilities, Current	1,347,000	0
Total liabilities	914,388,000	993,872,000
COMMITMENTS AND CONTINGENT LIABILITIES	0	0
Preferred stock, 20,000,000 shares authorized, $1 par value:
7.75% Series A cumulative redeemable preferred stock, $25 liquidation preference; 2,993,090 shares issued and outstanding in 2012 and 2011 and 7.50% Series B cumulative redeemable preferred stock, $25 liquidation preference; 3,791,000 shares issued and outstanding in 2012 and 2011	0	0
Common stock, $1 par value, 350,000,000 shares authorized, 220,255,676 and 220,082,610 shares issued in 2015 and 2014, respectively	220,256,000	220,083,000
Additional paid-in capital	1,722,224,000	1,720,972,000
Treasury stock at cost, 8,742,181 and 3,570,082 shares in 2015 and 2014, respectively	(134,630,000)	(86,840,000)
Distributions in excess of cumulative net income	(124,435,000)	(180,757,000)
Total equity	1,683,415,000	1,673,458,000
Total liabilities and equity	$ 2,597,803,000	$ 2,667,330,000